The present invention relates generally to a hermetic compressor and, more particularly, to such a compressor including intermeshing fixed and orbiting scroll members within a housing having an oil sump, wherein oil from the sump is used to lubricate and to help seal the scroll members.
A typical scroll compressor comprises two mutually facing scroll members, each having an involute wrap, wherein the respective wraps interfit to define a plurality of compression pockets. When one of the scroll members is orbited relative to the other, the pockets travel in a radial direction, e.g., from a radially outer suction port to a radially inner discharge port, to convey and compress a refrigerant fluid.
Several design problems are associated with scroll-type compressors of the type described herein. For example, a proper seal must be maintained at the sliding interface between the wrap tips of one scroll member and the face surface of the opposite scroll member in order to minimize leakage between compression pockets of different pressure levels. Such leakage causes reduced compressor operating efficiency. Likewise, proper lubrication is necessary at the sliding interface between scroll members in order to minimize friction. Excessive friction results in heating of the scroll members and increased drive torque requirements, both of which reduce the operating efficiency of the compressor.
It is generally recognized that the presence of oil at the sliding interface between scroll members improves sealing and reduces friction. However, several problems and disadvantages are associated with prior art compressors and associated methods for providing such oil at the interface. For example, an intentional high to low pressure leak is often created in order to draw the oil into the interface. This intentional leak between suction and discharge pressure regions reduces compressor operating efficiency. Also, oil introduced at the interface often becomes entrained in the refrigerant that is subsequently supplied to the accompanying refrigeration system. If the oil rate, i.e., the percentage of oil present in the refrigerant, becomes too high, the efficiency of the refrigeration system diminishes.
The present invention is directed to overcoming the aforementioned problems associated with hermetic scroll compressors, wherein it is desired to provide oil at the interface between scroll members in order to enhance sealing and reduce friction.